1. Field of the Invention
This invention generally relates to a display device and a repairing method and especially to a thin film transistor array and a repairing method thereof.
2. Description of Related Art
The rapid progress of the multi-media society is most likely benefited from the accelerated advancement of semiconductor devices or display devices. As for a display, the Thin Transistor Liquid Crystal Display (i.e. TFT-LCD) has become the trend in the market, owing to its superiorities in picture quality, space efficiency and low power consumption rate, and radiation-free, etc.
The Thin Transistor Liquid Crystal Display (i.e. TFT-LCD) is mainly consisted of a thin film transistor array, color filter substrate and liquid crystal layer. The thin film transistor array is consisted of thin film transistors arranged in multiple arrays and pixel electrodes corresponding with each thin film transistor. The thin film transistor is used as a switch element of the liquid crystal display unit. Moreover, in order to control the individual pixel unit, the particular pixel is selected through scan line and data line, and the corresponding display information of the pixel is displayed by providing a suitable operating voltage. Moreover, a portion of the area of the above mentioned pixel electrode normally covers the scan line or the common line to form a storage capacitor. In the conventional technology, the popular storage capacitors can be assorted into the Metal-Insulator-Metal (i.e. MIM) capacitor and the Metal-Insulator-ITO (i.e. MII) capacitor. The above two structures of storage capacitor will be described as follows.
FIG. 1 shows a cross-sectional view of a conventional storage capacitor with the MIM structure. In the conventional pixel structure as shown in FIG.1, the storage capacitor Cst with the MIM structure is created with the scan line or the common line 100 and an upper electrode 120, disposed above the scan line or the common line 100. And in the MIM storage capacitor, the scan line or the common line 100 is electrically insulated from the upper electrode with a gate insulating layer 110. Moreover, through the contact window 132 of a protective layer 130, the pixel electrode 140 is electrically connected with the upper electrode 120.
FIG. 2 shows a cross-sectional view of a conventional storage capacitor with the MII structure. In the conventional pixel structure of FIG.2, the storage capacitor of MII structure is created with the scan line or the common line 200 and a pixel electrode 230, disposed above the common line or the scan line 200. The difference between the storage capacitor with the MII structure and that with the MIM structure is that the scan line or the common line 200 in the MII structure is electrically insulated from the pixel electrode 230 through a gate insulating layer 210 and a protective layer 220.
In general, the emitting efficiency is better if that the aperture ratio of the pixel structure is larger. On the other hand, the photoelectric function of a liquid crystal display is better if the storage capacitance Cst is larger. However, with the conventional pixel structure of a liquid crystal display, the aperture ratio of the pixel structure can be decreased, if the storage capacitance Cst is increased by increasing the common line area. In order to increase the storage capacitance Cst without influencing the aperture ratio, the thickness of the gate insulating layer 210 and/or the protective layer 220 must decrease. However, the reliability of the thin film transistor element can be decreased, if the thickness of the gate insulating layer 210 and/or the protective layer 220 is decreased.
Furthermore, defects in the manufacturing process and other factors that causes particles falling into the gate insulating layer and/or the protective layer or cavities forming in the gate insulating layer and/or a protective layer can cause the capacitor leakage phenomenon. Therefore, the pixel display is abnormal and the display quality is poor.